Non-Volatile Memory Programming with Perturbation Pulse Thermalization
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Solution Overview
Problem
The challenge in programming non-volatile memory devices, particularly in charge trap flash memory, is the time-dependent change in threshold voltage due to thermalization of electrons in the charge trap layer, which complicates the control of threshold voltage distribution and can lead to verification errors and over-programming, increasing the voltage distribution in program states.
Innovation Solution
A method involving a two-step verification process using first and second verification voltages, with a perturbation pulse applied to facilitate thermalization of charges if the memory cell passes the first verification, and repeating the programming operations until the second verification is passed, thereby reducing over-programming and improving threshold voltage distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional single-step verification programming method is used, then the programming process is simple and fast, but threshold voltage distribution is poor due to verification errors and over-programming
Solution Approach 1:
The verification process is segmented into multiple steps with different verification voltages. The first verification uses a lower voltage to detect programming completion, while the second verification uses a higher voltage to detect over-programming. This segmentation allows the system to distinguish between different programming states and adjust the programming process accordingly, improving threshold voltage distribution without excessive complexity.
Solution Approach 2:
The programming method dynamically adjusts the verification voltage based on the programming state. By applying different verification voltages (first verification voltage and second verification voltage) at different stages, the system adapts to the changing threshold voltage characteristics during programming, enabling precise control of the programming process and reducing over-programming.
2Productivity
If programming speed is increased to improve productivity, then time-dependent threshold voltage changes cause more verification errors and over-programming
Solution Approach 1:
The method performs preliminary verification at an intermediate stage using the first verification voltage before final verification with the second verification voltage. This preliminary action allows the system to detect programming completion early and adjust the final verification accordingly, maintaining high programming speed while ensuring verification accuracy by catching potential over-programming issues.
Solution Approach 2:
The programming method incorporates feedback from both verification stages to control the programming process. The first verification provides feedback on programming completion, and the second verification provides feedback on over-programming. This multi-stage feedback mechanism allows the system to maintain reliability even at high programming speeds by continuously monitoring and adjusting the programming state.
3Measurement precision
If the verification voltage is increased to detect all programming states accurately, then over-programming occurs more easily because threshold voltage changes with time
Solution Approach 1:
The verification voltage is segmented into two distinct levels: a first verification voltage for detecting programming completion and a second verification voltage for detecting over-programming. This segmentation allows the system to use appropriate voltage levels for different verification purposes, maintaining measurement precision while preventing over-programming by using the lower first verification voltage for initial checks.
Solution Approach 2:
The method applies a partial verification action using the first verification voltage that is lower than the maximum possible verification voltage. This partial action is sufficient to detect programming completion but not high enough to cause over-programming. The second verification with higher voltage is applied only as a safety check, making the verification process both precise and protective against over-programming.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces the distribution of threshold voltage in program states by ensuring quicker thermalization of charges and minimizing errors, resulting in a more controlled and efficient programming process.
Implementation Method 1
The injected electrons are thermalized in a deep trap and spatially spread in a nitride film. Accordingly, because the threshold voltage of the CTF memory changes as the electrons are thermalized and spread in the nitride film
Implementation Method 2
a perturbation pulse may be applied to the memory cell to facilitate thermalization of charges in the memory cell
Data Source
AI summary
A method of programming a non-volatile memory device may include performing a first programming operation including applying a program voltage to a memory cell and verifying the memory cell using a first verification voltage. A perturbation pulse may be applied to the memory cell to facilitate thermalization of charges in the memory cell if the memory cell passes the verification using the first verification voltage. The memory cell may be verified using a second verification voltage greater than the first verification voltage after the perturbation pulse is applied.